Oil can be found admixed with a number of fluid streams, requiring its separation. For example, tailings ponds from oil sands processing contain a heavy oil called bitumen. Separating the bitumen from the tailings water can offer economic and environmental advantages. Refinery effluents can contain oil admixed with an aqueous stream. Bilge water and other types of industrial waste water can contain a quantum of oil admixed therein. Water used for or produced by hydraulic fracturing in oil or gas reservoirs can also contain a hydrocarbon component, for example crude oil. Water that is co-produced during oil production is typically treated by chemical and mechanical separation practices to recover the oil values and to minimize the contamination of the produced water effluent stream. After this conventional treatment, it is desirable to apply secondary treatment to meet environmental and regulatory objectives. Oil contaminated waters present challenges to treatment methods such as reverse osmosis, nanofiltration, ultrafiltration, diatomaceous earth filtration, activated carbon treatment, and the like. Removal of light chain and heavy chain hydrocarbons from aqueous fluid streams, including aliphatics, aromatics, and mixtures thereof, poses a significant challenge for oil drilling and production facilities and associated water treatment operations. It would be advantageous to provide efficient and cost-effective systems for separating the oil from the fluid stream.
As a salient example of oil contaminating an aqueous fluid stream, the Deepwater Horizon oil spill in 2010 demonstrated the challenges of separating these two components, and the damage that such oil contamination can cause. Oil floating in the open water decimates sea-faring birds and damages fish populations. When the oil approaches the shoreline, it coats the beaches, estuaries and wetlands, devastating living things that depend upon those habitats and wreaking immeasurable economic havoc. Once released, an oil spill proves very difficult to contain or deflect. Even more difficult is the task of removing it adequately from environmental contact.
Current methods of spill containment include physical and chemical approaches. For physical containment, booms or socks can be used, which act as barriers and which can have oil absorption capabilities. However, these mechanisms lose significant efficacy in the open ocean when conditions are rough, a situation that is not uncommon where oil spills occur. For chemical treatments, a variety of dispersants have been devised. Two significant drawbacks limit the efficacy of dispersant technologies. First, it is difficult to form stable microemulsions of the heavy crude that constitutes the spill. In essence, the oily blobs in the spill simply break up into smaller blobs when they encounter the dispersant, but the blobs do not disappear from the water surface. The smaller blobs can continue towards the shoreline with damaging effect. Second, even if stable microemulsions were achievable with a given dispersant, it is not clear that the emulsified system would cause less damage than the intact oil blobs. In fact, the emulsified oil system could spread more rapidly and widely, potentially amplifying the destruction.
To mitigate the potential damage of an open-water spill, it is desirable to cause the floating crude oil or other oily substance to be rapidly sequestered, for example by entrapment in a floating substrate. Alternatively, the floating oil or crude oil can be caused to sink rapidly and completely to the sea floor before it affects the marine population in the open ocean, and before it reaches landfall. Such approaches can offer the best chance of protecting vulnerable coastal fisheries and other ecosystems from the devastating impact of an open-ocean oil spill.